This P01 develops and applies state-of-the-art methods to analyze existing but under-utilized drug abuse databases in collaboration with their owners. We address contemporary, theoretical, and applied issues in drug abuse research to understand intersections between substance abuse and AIDS risk behaviors as well as minority and gender-based health disparities. We work with dozens of investigators from drug &social policy, epidemiology, health sciences, medicine, nursing, psychiatry, psychology, public health, and social work who own exciting substance abuse data to develop models that test current theories, especially on epidemiology, prevention, intervention, and treatment of drug abuse, using modern multivariate methods to control for measurement errors, biases, and other confounds. The Models and Methods Project develops psychometric and statistical analytic techniques that hold special promise for improving the quality of drug abuse and AIDS research. The At-Risk Project studies substance abuse related data sets on vulnerable populations (substance abusers, homeless people, individuals who are HIV positive or who have AIDS, victims of domestic abuse, runaways, gang members, and others at high risk for AIDS or drug abuse) with methods to control sampling, measurement, distributional and other biases. The Community Project studies drug abuse etiology, adult consequences, HIV risk, intergenerational processes, general deviance, and related issues in large community-based samples, and develops and tests explanatory theories using models that permit separation of common from specific effects, control for artifacts, etc. The Core Project oversees and integrates all components, hosts visiting scholars, provides computer facilities, and sponsors a mentoring program for disadvantaged students. The substantive part of the Models Project and the At-Risk and Community Projects will be developing and testing integrative theories that can be applied across different populations. The findings from their studies will lead to greater understanding of precursors and concomitants of substance abuse and HIV/AIDS risk and transmission. In turn, these findings will guide development of effective interventions to reduce negative health outcomes and treatment disparities in community, ethnic, and vulnerable populations, and provide guidance on how these may be alleviated.